This invention relates generally to a magnetic recording media and in particular to a record carrier wherein a clad protective layer is deposited on a substrate prior to the magnetic layer.
1. Field of the Invention
Magnetic recording media having thin films of a magnetizable metal or alloys thereof have found a usage in electronic data processing equipment as high storage capacity memories. Various forms of the substrate base such as films, drums, wires or disks are commonly used. The thin film metal-plated magnetic recording media permits a higher storage capacity from the usual iron oxide recording media.
Generally the magnetic layer is deposited on a substrate that is easily machinable such as an aluminum disk. But aluminum is soft and contains impurities that hinder fabricating the perfectly smooth surface required for the magnetic layer and a low flying magnetic recording transducer. Further, a galvanic action can occur between the aluminum substrate and the thin film magnetizable layer if the magnetizable layer is deposited directly onto the aluminum. The galvanic action causes a corrosion of the subsequent layer and with the magnetic layer causes recording errors. Thus, a clad layer is normally deposited onto the substrate before the magnetic layer to provide wear resistance and mechanical rigidity to the aluminum material, to provide an easily polishable layer for smoothness, and to protect the aluminum from corrosion. The protective layer together with any other undercoat layers such as a chromium layer should enhance the coercivity and other magnetic properties of the overlying magnetic thin film layer.
2. Prior Art
It is well known to insert a metal film between a substrate and a ferromagnetic material layer. It is also known as shown in U.S. Pat. No. 3,520,664 to D. P. York that a plurality of layers can be deposited intermediate the substrate and the magnetic layer. As with all of the prior art, the intent is to overcome the impurities in the substrate, to prevent galvanic action between the substrate and the magnetic layer, and to provide mechanical rigidity.
It is, therefore, an object of the present invention to provide a magnetic disk structure and a process for making a magnetic disk wherein the protective layer covers any asperities in the substrate, prevents galvanic action between the magnetic layer and the substrate, and provides a mechanical rigidity to the structure and allows for smoothing any asperities in the substrate.